The present invention relates to a method and apparatus for evaluating photographic color negatives prior to copying. More particularly, the invention relates to a method and apparatus for color analysis of negatives preparatory to integral color printing in order to ascertain the amounts of light in different colors to which a photographic paper or the like must be exposed in order to obtain satisfactory reproductions of color originals.
It is known to photoelectrically scan a color negative in order to ascertain the required quantities of light in each of the primary colors. Many presently known techniques for determination of the quantities of printing light in each of the primary colors are based on the premise that a satisfactory reproduction is obtained if one relies on the neutral grey principle independently of the color composition of the original. This holds true for a large number of originals, as long as an original does not exhibit so-called subject failure, i.e., one or more large areas of dominant color. Conventional proposals involve pronounced suppression of dominant colors by non-uniform evaluation of originals in different colors so that the copy again exhibits a neutral grey. Such proposals are unsatisfactory when a negative exhibits one or more large areas of dominant color.
It was further proposed to ascertain the quantities of copying light in the primary colors by scanning successive fields of a color negative and by attributing less importance to fields which exhibit a pronounced color imbalance, the assumption being that such fields form part of an area of dominant color. Reference may be had to German Offenlegungsschrift No. 2,535,034. The just discussed method exhibits the drawback that it leads to the making of unsatisfactory reproductions when a color negative comprises several areas of dominant color. Thus, the influence of such areas upon the selected quantities of printing or copying light in the primary colors is eliminated or reduced to such an extent that the coloration of the print deviates noticeably from the color composition of the photographed subject or scene. In other words, when the major part of a color negative exhibits one or more dominant colors, the portion of such negative which was evaluated and actually considered in the selection of quantities of copying light is only a small fraction of the entire negative, i.e., such small fraction is not representative of the color distribution of the original.